Patent GB-652780-A (GB)
Title: Improvements in and relating to liquid actuated prime mover speed regulating systems
IPC: F15B21/045
Filed: 1948-09-29
Abstract: 652,780. Turbines. BRITISH THOMSONHOUSTON CO., Ltd. Sept. 29, 1948, No. 25387. Convention date, Oct. 1, 1947. [Class 110(iii)] [Also in Group XXIX] A hydraulic governor for regulating the speed of a steam turbine driving pumps, compressors, fans &c. comprises a pump driven at a speed bearing a fixed ratio to that of the turbine and supplying pressure liquid to a hydraulic motor regulating the turbine speed through a line having a variable bleed orifice automatically controlled on changes in the viscosity of the operating liquid by compensating means having capillary and non-capillary restrictions in series and a duct therebetween, the pressure in which duct controls the amount of opening of the bleed to modify the action of the motor. As shown, a gear pump 16 driven by the turbine 1 supplies liquid through a line 14 to a hydraulic motor 7 having, a spring- loaded bellows 8 operatively connected to the turbine inlet valve 5 and to a branch line 18 provided with a bleed orifice 22, The orifice 22 is controlled by a needle valve 27 connected by levers 32, 35 and a link 34 to a second hydraulic motor 41 similar to the motor 7 and supplied with pressure liquid through a duct 42 disposed between an annular capillary restriction 49 formed between a cylindrical housing 44 and concentric cylinder 48 supported on radial arms 51 and a non-capillary restriction formed by a plate having a sharpedged orifice 53. The downstream side of the orifice 53 is conected to a chamber 46 having an atmospheric vent 47 and a drain pipe 26 leading to a tank 15 supplying the pump; whilst the upstream side of the restriction 49 is connected to a chamber 23 having a line 54 supplying lubricating oil to the turbine bearings and a line 24 having a relief valve 25 therein, so that the requisite pressure in the line 54 is attained. The operating speed of the turbine is adjustable by a screw 37 and the compensating effect on the needle valve 27 varied by the provision of holes 33a, 34a, 35a in the levers 32, 35. In operation, assuming no changes in the viscosity of the operating oil, any departure from the pre-set speed of the turbine will vary the speed of rotation of the pump 16 and hence the pressure acting on the bellows 8 to adjust the valve 5. Should, e.g., a rise in the temperature of the oil take place it will become less viscous resulting in increased flow through any leakage spaces in the pump and through the orifice 22 and reduced pressure in the line 14 with consequent increase in turbine speed. This results in an increased flow through the restriction 49 and a higher pressure in the duct' 42 since the flow through the orifice 53 will remain substantially constant. This higher pressure will act on the bellows of the motor 41 and through the levers 32, 35 and the link 34 to adjust the needle valve 27 towards closure to increase the pressure in the line 14 and hence' reduce the' turbine speed to its pre-set value. In a modification, the output pressure of a blower driven by the turbine acts on a further hydraulic motor to adjust through further linkage the lever 32 and hence the needle valve 27 to restore the blower pressure to its preset value.